1. Field of the Invention
The present invention relates, in general, to a magnetron and, more particularly, to a magnetron, in which a plurality of vanes positioned between a positive polar body and a negative polar section are radially arranged toward a central axis of the positive polar body, thereby generating microwaves.
2. Description of the Related Art
In general, magnetrons are high-frequency generators, and are widely used to generate microwaves in home appliances, such as microwave ovens, as well as in industrial applications, such as high-frequency heating apparatuses, particle accelerators and radars. In a magnetron, a plurality of vanes are arranged in a cylindrically shaped positive polar body toward a central axis of the positive polar body, and a negative polar section to emit thermions is positioned in the central axis of the positive polar body.
When power is supplied from an external power supply unit to the negative polar section, a filament of the negative polar section is heated and then the thermions are continuously emitted from the heated filament, so that a series of thermions are formed. Thereafter, the series of thermions are brought into contact with surfaces of inner ends of the vanes, after rotating around the filament and moving toward the surfaces of the inner ends of the vanes under the influence of an electric field and a magnetic field formed in an activating space defined between the filament and vanes. Thus, the series of thermions generate an electrical potential difference caused by alternating polarities in every two neighboring vanes. Accordingly, oscillations are continuously generated by electrical potential differences of alternating polarities in a plurality of resonant circuits formed between the positive polar body and the plurality of vanes, so that microwaves corresponding to a rotation speed of the series of thermions are generated.
The two neighboring vanes and a portion of the positive polar body connecting the two neighboring vanes to each other form a resonant circuit. When the magnetron is operated, electric charges move through the two neighboring vanes and the portion of the positive polar body connecting the two neighboring vanes to each other, and a movement direction of the electric charges is periodically and alternately changed. A frequency of the microwaves generated in the magnetron is determined by an alternation period of the movement direction of the electric charges.
When the electric charges move through the two neighboring vanes and the portion of the positive polar body during the operation of the magnetron, undesirable harmonics may be generated in the microwaves generated in the magnetron if a distribution of an electric field is not uniform on surfaces of outer ends of the vanes.